Insulating riser sleeve



FIG. 1 is a side elevational view of an insulating riser sleeve showing my new design;

FIG. 2 is a longitudinal sectional view taken in the direction of the arrows in line 2--2 of FIG. 3;

FIG. 3 is a top plan view thereof; and

FIG. 4 is a bottom plan view thereof. 

The ornamental design for an insulating riser sleeve, as shown. 